Presently, most commercially-available semiconductor diode lasers are fabricated of III-V compound semiconductors and their alloys. Such semiconductor diode lasers, which emit light in the infrared and red portions of the spectrum, are used inter alia as components in read and/or write heads of information processing equipment such as laser printers, bar code readers, and read and/or write devices for optical registration carriers such as CD and CD-ROM discs, and as transmitters in systems for optical glass fiber communication. In the latter systems, the semiconductor diode laser may also be used as a light amplifier, and in this application the term "laser" is meant to include such light amplifiers.
However, there are many applications for which the wavelength of light generated by infrared and red diode lasers is not suitable. Other types of semiconductor diode lasers, such as II-VI semiconductor diode lasers which emit light at shorter wavelengths, such as the green and blue portions of the spectrum, would accordingly be desirable. These semiconductor diode lasers would also increase the performance and capabilities of many systems which currently use infrared and red semiconductor diode lasers.
Contacts for applying a current to a semiconductor diode laser, whether of the III-V or II-VI type, are normally formed by electrode layers on both sides of the laser. These electrode layers preferably have a large surface area to allow for dissipation of heat which is generated during operation. However, current flow through the diode laser is desired only over a much smaller active area. Various techniques are known to adequately confine the current flow through semiconductor diode lasers, as shown for example in U.S. Pat. Nos. 4,454,603 and 5,213,998; Japanese Patents Nos. 1-218086 and 63-44786; and German Patent Application No. DE 3406361 A1.
Previously-known II-VI semiconductors diode lasers typically use polyimide or other dielectric materials to confine the current flow. This confinement of the current flow between the electrode layer and the contact layer is achieved in the prior art by a current-blocking layer of polyimide or other dielectric material which covers the contact layer and exposes only a small area of the contact layer through an opening. The electrode layer and the contact layer contact each other through this opening. The current flow between the electrode layer and the contact layer will thus only occur through the opening in the current-blocking layer, and will be blocked in the other areas where the current-blocking layer is present between the contact layer and the electrode layer. Due to the high temperatures, typically in the order of 300.degree. C.-400.degree. C., involved in the manufacture of II-VI semiconductor diode lasers having current-blocking layers of polyimide or other dielectric material, the prior art diode lasers are subject to degradation in the laser structure. This degradation can lead to operational failure, or a lasing action of lower quality or reliability.